Update git submodules

* Update docs/submodules/dovetail from branch 'master'
  - Change Bottlenecks volume mapping

    If mapping to host's /tmp, it won't clean all .log and .out files before
    run a new test. It causes the results file including all previous results.
    See https://build.opnfv.org/ci/view/dovetail/job/dovetail-apex-baremetal-default-mandatory-master/26/artifact/results/stress_logs/bottlenecks.stress.ping.out/*view*/
    It will affect the results check.

    Mapping to DOVETAIL_HOME/results/bottlenecks, which will always be cleaned
    before running another test.

    Change-Id: I22bfc871d6f041ae38308bf8e8f685993a376973
    Signed-off-by: xudan <xudan16@huawei.com>

diff --git a/docs/submodules/dovetail b/docs/submodules/dovetail
index 8e2c2b4..e79f851 160000 (submodule)
--- a/docs/submodules/dovetail
+++ b/docs/submodules/dovetail
@@ -1 +1 @@
-Subproject commit 8e2c2b42dff66d9896bfc5a8da8ee86cb18e8cb8
+Subproject commit e79f851c5b804db5884be05a50bc3ae0abe222b4